Earnings Per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	5.5	5.7	5.7	5.6
Share Options and Appreciation Rights [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	1.5	1.7	1.5	1.7
Novested Restricted Shares and Restricted Share Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares (in shares)	4.0	4.0	4.2	3.9